1. Field of the Invention
The present invention relates to an equipment for storing blood, sorting out various kinds of and a great deal of blood.
2. Description of Related Art
In order to store blood stably over a long period, it is necessarry to freeze blood at a very low temperature less than -135.degree. C., that is, the recrystallization temperature of ice. As a device for storing a great deal of blood in such purpose for transfusion or the like, a Dewar bottle has conventionally been used, as shown in FIG. 1.
In FIG. 1, numeral 21 is an inner globe which is in a globular shape having an opening on a side and holds liquefied nitrogen 20 within. The inner globe 21 is supported in an outer globe 22 which is a little larger than it and of substantially a similar figure with it, by a plurality of supporting members 23 provided between both globes substantially concentrically therewith. A space 24 formed between the inner globe 21 and the outer globe 22 is kept at a high vacuum by the action of a low temperature absorbent 25 held in a space which is formed at the bottom of the inner space 21 and communicates with the space 24. The inner globe 21 and the outer globe 22 are supported in a housing 26 by a support spring 27 provided between the housing 26 and the outer globe 22 with an opening portion upside. The opening portion is hermetically sealed by a lid 28. The stored blood is packed separately and held in a retainer 29 provided with a handle 29a, and inserted in the inner globe 21 together with the retainer 29 where the blood is stored being immersed in liquefied nitrogen 20 of -196.degree. C. that is by far less than the recrystallization temperature of the ice.
In the Dewar bottle, the evaporation of the liquefied nitrogen 20 held in the inner globe 21 is prevented by maintaining the space 24 at a highly vacuum condition and restraining the heat transmission through this space. It, however, is difficult to fully prevent the evaporation, and it is necessary to replenish liquefied nitrogen by the degree of decrease, usually watching the residual quantity of the liquified nitrogen 20. The Dewar bottle has such disadvantages that not only this replenishing work is troublesome but also that equipments such as a tank for holding a great deal of liquefied nitrogen to be used for replenishing are required.
As a device for storing microbes, cells and the like in laboratories in the area of biotechnology, a very low temperaure freezer has been put to practical use wherein multiple freezing cycle is made use of, and this device can be used as a blood storing device. In this very low temperature freezer, vapor compression refrigerating machines having different refrigerants are used in multistage combination. Therefore, it has such disadvantages that the cost of equipment is high, the performance coefficient is low at a very low temperature and the running cost is high. In addition, because of the limit in the lowness in temperatures to be obtained the recovery rate of blood is low, in contrast with the Dewar bottle. Therefore, such a freezer is not suitable for a device for storing a great deal of blood.